问题 实验题

小明和小刚用细棉线连接了两个纸杯制成了一个“土电话”。

(1)他们用“土电话”能实现10m间的通话,这表明                 

(2)细金属丝连接“土电话”,则听到的声音就大些.这一实验表明                

(3)如果用“土电话”时,另一个同学捏住棉线的某一部分,则听的一方就听不到声音了,这是由于                               

(4)如果在用“土电话”时.线没有拉直而处于松弛状态.则听的一方通过棉线         (选填“能”或“不能”)听到对方的讲话。

(5)潜艇失事时,艇员用硬物连续敲击潜艇钢板,三声短,三声长,再三声短(这是国际求救信号SOS的电报码)。救援人员如在附近,就可以知道潜艇中还有人在,这是因为_______

答案

(1) 固体(细棉线)可以传声;

(2)细金属丝比细棉线传声效果好;

(3) 声音在传播过程中被阻断;

(4) 不能;

(5) 固体(钢板)、液体(海水)可以传声。

单项选择题
阅读理解

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Damage to Ozone layer Gets Worse

In the middle of winter, when snow is falling in many parts of the United States, scientists have sounded a warning to people who plan to spend many hours in the sun this summer. The warning is: The sun’s summertime rays are more dangerous than once thought.

A team of scientists from 80 nations recently reported to the United Nations that a layer of ozone (臭氧层) in the atmosphere, which protects humans from harmful levels of ultraviolet radiation(紫外线辐射), will be thinner over the United States this summer. The thinner layer allows more ultraviolet rays from the sun to reach Earth. The extra amount of ultraviolet radiation could cause an increase in the number of cases of skin cancer.

Scientists first became concerned about the ozone layer in the mid-1980s when a hole was discovered in the layer above Antarctica during the winter. The hole was caused by chemicals used in refrigerators and air conditioners. When these chemicals are sent out into the atmosphere, they produce gases that destroy the ozone.

Concern about the protective ozone layer rose more recently when data(数据) from satellites and ground stations showed that ozone levels were dropping over areas other than Antarctica. Low ozone levels were recorded in the spring and summer over the United States and over other populated areas in the world.

Although many countries have already begun stopping the use of ozone destroying chemicals, the new findings are expected to advance the timetable for a total ban(禁止) of the chemicals.

59.   The scientists have observed the ozone layer_____.

A.  since 1980             B.  since last winter      

C.  for about 20 years       D.  for about one year

60. The ozone layer in the atmosphere can _____.

A.  do a lot of good to human beings in many ways.

B.  protect humans from diseases caused by bad weather.

C.  do a lot of harm to human beings in the summer-time.

D.  protect humans from harmful levels of ultraviolet radiation.

61. Scientists first found that there was a hole in the ozone layer_____.

A.  above Arctic during the winter in the mid-1980s

B.  above Antarctica during the winter in the mid-1980s

C.  over somewhere in the north of the equator in 1980

D.  over the U.S.A in the summertime in the mid-1980s

62.   The damage to the ozone layer was caused by_____.

A.  the changeable weather

B.  ozone-destroying chemicals

C.  chemicals from refrigerators

D.  chemicals from air conditioners